Study Year 1: Primary endpoint: To investigate the efficacy of each of two doses of adefovir dipivoxil compared to placebo with respect to improvement of liver histology. Study Year 2: To investigate the efficacy of one vs. two years of each of two doses of adefovir dipivoxil in the improvement of liver histology, HBeAg and HBsAg loss and seroconversion, sustained HBV DNA suppression and ALT normalization.